Necessary and sufficient condition for the equivalence of two pure multipartite states under stochastic local incoherent operations and classical communications

The resource theory of quantum coherence originated like entanglement in quantum information theory. However, until now proper classification of quantum states is missing under coherence. In this work we have provided a classification of states under local incoherent operations. We have succeeded in deriving the necessary and sufficient condition for which two pure multipartite states are equivalent under stochastic local incoherent operations and classical communications (SLICC) and local incoherent operations and classical communications (LICC). In particular, we have succeeded in characterizing three-qubit pure states under SLICC. Our result reveals the existence of an infinite number of SLICC inequivalent classes for three-qubit systems.